With the rapid development of the Internet technologies, there are increasingly abundant information resources on the Internet. Search engines provide great convenience to net users to quickly find required information on the Internet. In addition, with the increasing quantity of resources on the Internet and the accumulation of user behavior data in search engines, search engines provide capability to automatically answer questions. Compared with the conventional search engines, the search result of an automatic question answering system is answers directly extracted from related web pages, rather than a list of ordered web pages. The user no longer needs to spend time to search for answers in the web pages, thereby saving time for the user.
A content indexed by an automatic question answering system is no longer the content of an entire web page, but a paragraph or several sentences comprising a question and an answer in the content of the web page. As only a small quantity of resources naturally existed on the Internet comprise questions and answers, there is a need to extract information comprising questions and answers from the contents of web pages.